Apparatuses and methods for handling attach procedure in a mobile communication system

ABSTRACT

A user equipment for handling an attach procedure with a service network is provided. In the user equipment, a wireless module transmits an attach request message to the service network and receives an attach accept message replied to the attach request message from the service network, while a controller determines whether to accept the attach accept message according to a first parameter accompanying the attach accept message and sends an attach complete message, via the wireless module, to the service network in response to the attach accept message being accepted.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/465,824, filed on May 14, 2009 and entitled “Apparatus, System, andMethods for Handling Attach Procedure in Mobile Communication System”,now U.S. Pat. No. 8,135,404, which claims the benefit of U.S.Provisional Application No. 61/101,147 filed on Sep. 29, 2008 andentitled “Pseudo-CR on The UE does not accept ACTIVATE DEFAULT EPSBEARER CONTEXT REQUEST in attach procedure”, the entirety of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to handling an attach procedure, andmore particularly, to apparatuses and methods for handling an attachprocedure in a mobile communication system environment.

2. Description of the Related Art

In a typical mobile communication system environment, a mobile userequipment (UE) communicates with one or more mobile communicationsystems via the radio access networks of the mobile communicationsystems. A UE comprises various types of equipment such as a mobiletelephone (also known as cellular or cell phone), a laptop with wirelesscommunication capability, a personal digital assistant (PDA) etc. Theequipment may be portable, handheld, pocket-sized, and installed in avehicle etc and communicate voice and/or data signals with the radioaccess network.

A universal mobile telecommunications system (UMTS) is a thirdgeneration mobile communication system that has evolved from the GlobalSystem for Mobile communications (GSM) system. The UMTS is a Europeanstandard which aims to provide better mobile communication servicesbased on the GSM core network and wideband code division multiple access(W-CDMA) technology. Although UMTS delivers high data transfer rates,wireless data usage is expected to increase significantly over the nextfew years. For this reason, concepts for UMTS Long Term Evolution (LTE)have been proposed and the objective is to further improve UMTS toachieve high-data-rates, low-latency and packet-optimized radio accesstechnology. The improved UMTS technology is called Evolved UniversalTerrestrial Radio Access (E-UTRA) and the system employing the E-UTRAtechnology is called an Evolved Packet System (EPS).

For a UE, which complies with the 3GPP specifications for the E-UTRAprotocol, the 3GPP TS 24.301 specification, v.1.0.0, referred to hereinas the 24.301 specification, addresses the subject of theNon-Access-Stratum (NAS) protocol requirements for the EPS and the UE.

After the UE is powered on and connects to the EPS, it will need toperform an attach procedure to register itself to the EPS so that it canstart a packet data session over the EPS. As illustrated in FIG. 1, theattach procedure starts by the UE sending an ATTACH REQUEST message tothe EPS (step S101). The ATTACH REQUEST message may be sent combinedwith a PDN CONNECTIVITY REQUEST message indicating that the UE wishes tostart a packet data session with the EPS. When the EPS receives theATTACH REQUEST message, it authenticates the UE, checks if the UE isauthorized to have access to packet data services, and performs asecurity mode control procedure to activate the encryption on subsequentmessages (step S102). If none of the checks fails, the EPS accepts theattach request by sending an ATTACH ACCEPT message to the UE. The ATTACHACCEPT message may be sent combined with an ACTIVATE DEFAULT EPS BEARERCONTEXT REQUEST message if the PDN CONNECTIVITY REQUEST message is foundin the ATTACH REQUEST message (step S103). The ACTIVATE DEFAULT EPSBEARER CONTEXT REQUEST message contains the configuration used toactivate the default bearer for the packet data session. When the UEreceives the ATTACH ACCEPT message, it checks the ACTIVATE DEFAULT EPSBEARER CONTEXT REQUEST message to see if the configuration within isacceptable. If the UE accepts the configuration specified in theACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message, it applies theconfiguration, resets the counters associated with the attach procedure,including the attach attempt counter and the tracking area updatingattempt counter, enters the EMM-REGISTERED state, and sets the EPSupdate status to EU1 UPDATED (step S104). The UE then responds to theEPS with an ATTACH COMPLETE message to acknowledge that it has receivedand accepted the ATTACH ACCEPT message (step S105). The ATTACH COMPLETEmessage may be sent combined with an ACTIVATE DEFAULT EPS BEARER CONTEXTACCEPT message indicating that the UE has accepted the configuration ofthe default bearer from the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUESTmessage. At last, the EPS receives the ATTACH COMPLETE message combinedwith the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT message and theattach procedure ends successfully.

BRIEF SUMMARY OF THE INVENTION

Accordingly, embodiments of the invention provide an apparatuses andmethods for handling attach procedure in a mobile communication system.In one aspect of the invention, a user equipment handling an attachprocedure with a service network is provided. The user equipmentcomprises a wireless module and a controller. The wireless moduletransmits an attach request message to the service network and receivesan attach accept message replied to the attach request message from theservice network. The controller determines whether to accept the attachaccept message according to a first parameter accompanying the attachaccept message and sends an attach complete message, via the wirelessmodule, to the service network in response to the attach accept messagebeing accepted.

In another aspect of the invention, a method for a user equipment tohandle an attach procedure with a service network is provided. Themethod comprises sending an attach request message to the servicenetwork, receiving an attach accept message replied to the attachrequest message from the service network, determining whether to acceptthe attach accept message according to a first parameter accompanyingthe attach accept message, and sending an attach complete message to theservice network in response to the attach accept message being accepted.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescriptions of specific embodiments of an apparatuses and methods forhandling an attach procedure in an E-UTRA system environment.

BRIEF DESCRIPTION OF DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a message sequence chart illustrating a successful attachprocedure in an EPS environment;

FIG. 2 is a block diagram illustrating a UE in accordance of anembodiment of this present invention;

FIG. 3 is a message sequence chart illustrating the UE and EPS handlingan attach procedure according to an embodiment of the invention; and

FIG. 4 is a message sequence chart illustrating the UE and EPS abortingan unaccepted attach procedure after a predetermined number of retriesaccording to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims. In order to give better examples,the embodiments described below are utilized in EPS environments. Inaddition, 3GPP specifications are used to teach the spirit of thisinvention but not used to limit the scope of the present invention.

There are situations where the UE may not accept the configurationspecified in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message.For instance, if the bearer resources of the UE are not sufficientenough to apply a required configuration, there may be semantic errorsor syntactical errors in the configuration. Additionally, othersituations specified in clause 6.4.1. 4 of the 24.301 specification mayalso occur. If the UE does not accept the configuration, it requests asuitable or correct configuration from the EPS. Accordingly, the UEreinitiates the attach procedure. Yet, in accordance with clause5.5.1.2.4 of the 24.301 specification, whenever the UE receives theATTACH ACCEPT message combined with the ACTIVATE DEFAULT EPS BEARERCONTEXT REQUEST message, it resets the attach attempt counter andtracking area updating attempt counter, enters the EMM-REGISTERED state,sets the EPS update status to EU1 UPDATED, and applies the configurationspecified in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message.After, the UE sends an ATTACH COMPLETE message combined with theACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT message to the EPS. Thus,since the clause 5.5.1.2.4 of the 24.301 specification completelyignores the situation when the UE does not accept the configurationspecified in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message,faulty handling of attach procedures by the UE and EPS may occur.

FIG. 2 is a block diagram illustrating a UE in accordance of anembodiment of this present invention. The UE 210 has a wireless module211 for receiving and transmitting messages propagated in radiofrequency. The UE 210 also includes the NAS protocol stack 212, which isconnected to receive and transmit messages from and to the EPS 220 viathe wireless module 211. The connection between the NAS protocol stack212 and the wireless module 211 may involve protocol stacks that are notshown in FIG. 2, such as the radio resource control (RRC) protocolstack, the radio link control (RLC) protocol stack, the medium accesscontrol (MAC) protocol stack, and the physical layer protocol stack. Forimplementation, any of the protocol stacks referred to in thisspecification may be realized by a combination of hardware and software.The NAS protocol stack 212 comprises a controller 213 for performing theNAS functions and handling an attach procedure. The operation of thecontroller 213 is explained in more detail in the following embodiments.

FIG. 3 is a message sequence chart illustrating the UE and EPS handlingan attach procedure according to an embodiment of the invention. Duringthe attach procedure, the UE 210 maintains an attach attempt counter,referred to herein as a retry counter, to keep track of the number ofretries allowed when the attach attempt is not successful. Initially,the retry counter is set to 0 (step S301). When the UE 210 wishes toregister with the EPS 220 and start a packet data session with the EPS220, the UE 210 initiates an attach procedure by sending an ATTACHREQUEST message, with a PDN CONNECTIVITY REQUEST message combined in it,to EPS 220 (step S302). After reception of the ATTACH REQUEST message,the EPS 220 performs the authentication procedure to check if the UE 210is authorized, and the security mode control procedure to activate theencryption on the subsequent messages in the connection with UE 210(step S303). If the procedures end normally, the EPS 220 sends an ATTACHACCEPT message, with an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUESTmessage combined in it, to the UE 210 (step S304). Upon reception of theATTACH ACCEPT message by the wireless module 211, the controller 213retrieves the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message anddetermines that the default EPS bearer context activation configurationin the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message is notacceptable due to the reasons as specified in clause 6.4.1. 4 of the24.301 specification (step S305). The UE 210 then checks to see if theretry counter is less than a predetermined number. If the retry counteris less than a predetermined number, the UE 210 resends the ATTACHREQUEST message combined with the PDN CONNECTIVITY REQUEST message (stepS306). The resent ATTACH REQUEST message includes a resent cause (IE“Resent cause”) indicating that the message is resent due to theprevious ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message beingrejected by UE 210, and the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUESTmessage includes an unaccepted cause (IE “ESM cause”). Upon resendingthe ATTACH REQUEST message, the UE 210 increments the retry counter by 1(step S307). When the EPS 220 receives the resent the ATTACH REQUESTmessage, it checks to see if the ATTACH REQUEST message includes aresend cause. If the ATTACH REQUEST message includes a resend cause, theEPS 220 aborts the current attach procedure and initiates a new attachprocedure (step S308) by sending a new ATTACH ACCEPT message combinedwith a new ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message to the UE210 (step S309). The configuration specified in the new ACTIVATE DEFAULTEPS BEARER CONTEXT REQUEST message is adjusted by EPS 220 according tothe unaccepted cause. Since the configuration specified in the newACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message is adjusted, the UEmay accept the new ATTACH ACCEPT message and the new ACTIVATE DEFAULTEPS BEARER CONTEXT REQUEST message. After accepting the new ATTACHACCEPT message, the UE 210 continues with resetting the attach attemptcounter and tracking area updating attempt counter, entering anEMM-REGISTERED state, setting the EPS update status to EU1 UPDATED, andapplying the configuration specified in the new ACTIVATE DEFAULT EPSBEARER CONTEXT REQUEST message (step S310). Afterward, the UE sends anATTACH COMPLETE message combined with the ACTIVATE DEFAULT EPS BEARERCONTEXT ACCEPT message to the EPS (step S311). Once the EPS 220 receivesthe ATTACH COMPLETE message, the attach procedure ends successfully.

In other embodiments, the UE 210 may rejects the new ATTACH ACCEPTmessage again and thus the operations in step S305˜S307 are repeated. Inthis case, step S305˜S307 can be repeated, until the retry counter isgreater than or equal to the predetermined number or the UE 210 acceptsthe new ATTACH ACCEPT message.

FIG. 4 is a message sequence chart illustrating the UE and EPS abortingan unaccepted attach procedure after a predetermined number of retriesaccording to an embodiment of the invention. During an attach procedure,the UE 210 carries out the retry process by resending the ATTACH REQUESTmessage with a resent cause (step S401), as depicted in FIG. 3, when notaccepting the ATTACH ACCEPT message from the EPS 220. Upon resending theATTACH REQUEST message, the UE 210 increments the retry counter by 1(step S402). When the EPS 220 receives the resent ATTACH REQUEST messagewith the resent cause, it responds accordingly by aborting the currentattach procedure and reinitiating a new attach procedure (step 5403) bysending a new ATTACH ACCEPT message combined with a new ACTIVATE DEFAULTEPS BEARER CONTEXT REQUEST message to the UE 210 (step S404). If the UE210 rejects the ATTACH ACCEPT message again (step S405), then the retryprocess (step S401˜S404) repeats. The maximum number of retries can beany predetermined number, or 5 in this embodiment. If the retry processfails for 4 more times (step S406) which means the maximum number ofretries has been reached, then the UE 210 aborts the attach procedure bysending a DETACH REQUEST message to the EPS 220 (step S407). Uponreceiving the DETACH REQUEST message, the EPS 220 aborts the attachprocedure (step S408) and responds by sending a DETACH ACCEPT message tothe UE 210 (step S409). Afterward, the attach procedure ends by beingconsidered as failed by both the UE 210 and the EPS 220.

While the invention has been described by way of example and in terms ofpreferred embodiment, it is to be understood that the invention is notlimited thereto. Those who are skilled in this technology can still makevarious alterations and modifications without departing from the scopeand spirit of this invention. Therefore, the scope of the presentinvention shall be defined and protected by the following claims andtheir equivalents.

What is claimed is:
 1. A user equipment, handling an attach procedurewith a service network, comprising: a wireless module configured totransmit an “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message inaccordance with the 3rd Generation Partnership Project (3GPP) technicalspecifications to the service network and configured to receive anattach accept message replied to the “ACTIVATE DEFAULT EPS BEARERCONTEXT REQUEST” message from the service network; and a controllerconfigured to determine whether to accept the attach accept messageaccording to a first parameter accompanying the attach accept message,and in response to the attach accept message not being accepted, thecontroller configured to resend, via the wireless module, the “ACTIVATEDEFAULT EPS BEARER CONTEXT REQUEST” message with a Resent causeInformation Element (IE) indicating that the “ACTIVATE DEFAULT EPSBEARER CONTEXT REQUEST” message is being resent due to the attach acceptmessage not being acceptable, to the service network, thereby enablingthe service network to adjust the first parameter to be included inanother attach accept message corresponding to the resent attach acceptmessage.
 2. The user equipment of claim 1, wherein the attach requestmessage is accompanied with a packet data network connection request. 3.The user equipment of claim 2, wherein the packet data networkconnection request is used to request a connection to an Evolved PacketSystem in accordance with the 3rd Generation Partnership Project (3GPP)technical specifications.
 4. The user equipment of claim 1, wherein therequest conforming to “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” isfor negotiating bearer configuration.
 5. The user equipment of claim 1,wherein the controller performs at least one of the following steps inresponse to the attach accept message being accepted: resetting anattach attempt counter and a tracking area updating attempt counter;entering an EMM-REGISTERED state; setting an EPS update status to EU1UPDATED; and applying configuration specified in the first parameter,wherein the EMM-REGISTERED state and EU1 UPDATED state are in accordancewith the 3rd Generation Partnership Project (3GPP) technicalspecifications.
 6. The user equipment of claim 1, wherein the wirelessmodule is further configured to send an attach complete message to theservice network in response to the attach accept message being accepted.7. The user equipment of claim 6, wherein the attach complete message isaccompanied with a second parameter corresponding to the firstparameter.
 8. The user equipment of claim 7, wherein the secondparameter is comprised in a response conforming to “ACTIVATE DEFAULT EPSBEARER CONTEXT ACCEPT” in accordance with the 3rd Generation PartnershipProject (3GPP) technical specifications.
 9. The user equipment of claim8, wherein the response conforming to “ACTIVATE DEFAULT EPS BEARERCONTEXT ACCEPT” is for informing the service network of the acceptanceof the first parameter.
 10. A method for a user equipment to handle anattach procedure with a service network, comprising: sending an“ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” in accordance with the 3rdGeneration Partnership Project (3GPP) technical specifications messageto the service network; receiving an attach accept message replied tothe “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message from theservice network; determining whether to accept the attach accept messageaccording to a first parameter accompanying the “ACTIVATE DEFAULT EPSBEARER CONTEXT REQUEST” message; and in response to the attach acceptmessage not being accepted, resending the “ACTIVATE DEFAULT EPS BEARERCONTEXT REQUEST” message with a Resent cause Information Element (IE)indicating that the “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST”message is being resent due to the attach accept message not beingacceptable, to the service network, thereby enabling the service networkto adjust the first parameter to be included in another attach acceptmessage corresponding to the resent attach accept message.
 11. Themethod of claim 10, wherein the attach request message is accompaniedwith a packet data network connection request.
 12. The method of claim11, wherein the packet data network connection request is used torequest a connection to an Evolved Packet System in accordance with the3rd Generation Partnership Project (3GPP) technical specifications. 13.The method of claim 10, wherein the request conforming to “ACTIVATEDEFAULT EPS BEARER CONTEXT REQUEST” is for negotiating bearerconfiguration.
 14. The method of claim 10, further comprising performingat least one of the following steps in response to the attach acceptmessage being accepted: resetting an attach attempt counter and atracking area updating attempt counter; entering an EMM-REGISTEREDstate; setting an EPS update status to EU1 UPDATED; and applyingconfiguration specified in the first parameter, wherein theEMM-REGISTERED state and EU1 UPDATED state are in accordance with the3rd Generation Partnership Project (3GPP) technical specifications. 15.The method of claim 10, further comprising sending an attach completemessage to the service network in response to the attach accept messagebeing accepted.
 16. The method of claim 15, wherein the attach completemessage is accompanied with a second parameter corresponding to thefirst parameter.
 17. The method of claim 16, wherein the secondparameter is comprised in a response conforming to “ACTIVATE DEFAULT EPSBEARER CONTEXT ACCEPT” in accordance with the 3rd Generation PartnershipProject (3GPP) technical specifications.
 18. The method of claim 17,wherein the response conforming to “ACTIVATE DEFAULT EPS BEARER CONTEXTACCEPT” is for informing the service network of the acceptance of thefirst parameter.